Drafting apparatus



March 1955 a. s. SHEINWALD 2,703,463

DRAFT ING APPARATUS Filed Sept. 18, 1952 1 I 3 5 Sheets-Sheet 1 ATTORNEYS March 8, 1955 B. s. SHEINWALD 2,703,468

DRAF'I'ING APPARATUS Filed Sept. 18, 1952 5 Shaets-Shaet 3 March 1955 a. s. SHEINWALD 2,703,468

DRAFTING APPARATUS Filed Sept. 18, 1952 5 Sheets-Sheet 4 INVENTOR AT'II )RNEYS March 8, 1955 Filed Sept. 18, 1952 B. s. SHEINWALD ,70 ,468

DRAFTING APPARATUS 5 Sheets-Sheet 5 IIII'IIIII news/W d AELlflO/KSV/P or "000 05 a; 42057707) 10 DEM5/7Y RATIO/4ND DENSITY fa? arisen/7 MIIZ'EHLS.

INVENTOR ABEMMM/N 6f SYEINWD ATTORNEYS United States Patent Office DRAFI'ING APPARATUS Benjamin S. Slleinwlld, Brookline, Mm.

Application September 18, 1952, Serial No. 310,160

15 Claims. (Cl. 45-131) The present invention relates to drafting apparatus and more particularly to drafting boards provided with a continuous-belt drafting surface.

It has heretofore been proposed to facilitate drafting operations by providing a movable drafting member in the form of an endless belt upon which the drafting paper, cloth and the like, hereinafter sometimes referred to as work paper, may be secured. Instead of bending far over a drafting board to read: upper portions of the work paper, or taking time to remount the paper to permit convenient drafting at different positions thereof, the draftsman merely moves the paper to the desired extent by rotating the belt. Such devices have not, however, met with commercial success principally because a satisfactory belt material has not heretofore been utilized. Proper mechanical constructions for using such a belt have also not previously been devised. These unsuccessful prior-art proposals embody belts of paper and the like that are subject to appreciable stretching, temperature and humidity changes, soiling, permanent markings such as pencil grooves and compass holes, and other disadvantages. Some'only of these disadvantages have been at least partially overcome with stationary board coverings, as of linoleum, cork and linseed oil, as well as cork-paint mixtures. These stationary board coverings are not adapted, however, for use as belts.

An object of the present invention, therefore, is to provide a new and improved drafting apparatus of the character described.

A further object is to provide a new and improved drafting member that is not subject to any of the abovementioned disadvantages and that is particularly adapted for use as a drafting belt.

In accordance with the invention, a flexible resilient plastic belt material is utilized having a density of between about 0.85 and 1.42, a ratio of modulus of elasticity-to-density substantially equal to, or less than, about 600,000, a surface hardness on the Rockwell M-scale of preferably between 35 and 50, and a preferable thickness of from about 0.02 to 0.25, where the density is expressed in units of grams per cubic centimeter, the modulus of elasticity in units of pounds per square inch, and the units of thickness in inches. Preferred apparatus for operating such a belt is later described in detail as are preferred plastic materials.

Other and further objects will be discussed hereinafter and will be more particularly pointed out in the appended claims.

The invention will now be explained in connection with the accompanying drawings:

Fig. 1 of which is a perspective view of a drafting apparatus constructed in accordance with a preferred embodiment of the invention and partly broken away to illustrate details of constructions;

Fig. 2 is a fragmentary side elevation, partly in sec tion and upon an enlarged scale, of the leg-supporting structure of the apparatus of Fig. 1;

Fig. 3 is a plan view of the apparatus of Fig. 1;

Fig. 4 is a side elevation of the apparatus of Figs. 1 and 3, looking at the left-hand side in Fig. 1;

Fig. 5 is a section taken upon the line 5-5 of Fig. 3, looking in the direction of the arrows;

Fig. 6 is an underside plan of the apparatus with the legs thereof in section;

Fig. 7 is a section taken u n the line 7-7 of Fig. 4, looking in the direction of e arrows;

Fig. Sisaperspectiveviewofadetail;

. Fig. 12 is a graph illustrating the properties of different belt materials.

Referring to Fig. 1, an endless belt 1 of suitable material, hereinafter described, is shown carrying a drafting paper or other work sheet 3 that may be secured to the top surface of the belt as by Scotch tape or other adhesive 5. The belt 1 passes over three rollers 7, 9 and 11. The rollers 7 and 9 may, for example, be rubbercoated rollers supported between respective bracket members 13; and 15 extenfling from and secured tio ends 0 two opposite y disposed pressed stee es Upon the upper surfaces of the angles 2 is disposed a drawing board 17, as of wood, which may be secured to the angles by screws 45. The brackets 13 and 15 are each of Lshape in order to receive the ends of the board, as .shown more particularly in Fig. 4, with the rollers 7 and 9 supported slightly below the upper surface of the board 17. Joining the brackets 13 at the corresponding ends of the angles 2 is a cylindrical cover shield 19 for the roller 7. The brackets 15 are interconnected by a member 21, that may be integral therewith, spaced from the roller 9. To this member 21 may be secured drafting-machine clamps, lamps and other equipment. The third or auxiliary roller 11 is ported at its ends by further tensioning brackets 23 of triangular shapethat are centrally supported by a indie 25 passing through rectangular plates 27 seen: to and depending below the sides of the angles 2 near the ends carrying the roller 9. Near the upper vertex of each triangular-shaped tensioning bracket 23, a curved slot 29 is provided through which a locking screw 31 is passed to lock the bracket 23 to the plate 27 at any desired angular orientation within the curved slot 29. In this manner the position of the auxiliary roller 11 below the angles 2 and within the belt 1 may be adjusted so that the auxiliary roller 11 bears tightly against the inner surface of the belt 1 and thus tensions the same over the rolls 7 and 9 and over the top surface of the drawing board 17. Each of rolls 7, 9 and 11 may be mounted in ball bearings, not shown. Each roller is provided at its ends with a recess 33 within which the supporting pin 35 is received and locked as by a set screw 37 threaded within a locking plate 39 secured to the ends of the roller. The outer end of the supporting pin 35 IS positioned to prevent lateral movement by a locking collar 4, secured as by a set screw. The shaft 25 may be similarly mounted.

The belt 1 may be moved back and forth over the board 17 by actuating a hand-operated driving mechanrsm 37 connected outside the brackets 13 to the porting pins 35 of the roller 7. If, desired, of eoursefx mechanism 37 may be motor driven as with the aid of any well-known electric motor, not shown, the rotation of which may be rapidly started and stopped by switch controls and the direction of rotation of which may be rapidly changed. The draftsman may thus either by hand or'by motor rotate the mechanism 37 to carry the work paper 3 to any desired position, as more particularly illustrated in Figs. 9 to ll. In Fig. 9, the draftsman has adjusted the position of the belt 1 so that the top part only of the paper 3 is immediately in front of him. In Fig. 10, he has rotated the mechanism 37 clockwise to bring the full sheet 3 in view upon the board 17. In Fig. 11, he has carried the sheet still further in the direction of the right-hand arrow of Fig. 10 to bring the bottom portion of the sheet 3 directly in front of the draftsman. He could, of course, reverse the direction of rotation of the mechanism 37 in the direction of the left-hand arrow of Fig. 10 to bring the sheet back to the position shown in Fig. 9. In this manner, any intermediate position of the belt may, of course, also be attained. The sheet 3, moreover, may be longer than the length of the top portion of the belt 1 between the rollers 7 and 9, and may, indeed, extend for the complete length of the belt, thus permitting work to be done on a sheet slightly more than twice the size of the board 17. In all cases, the draftsman may remain seated, and the work may be moved to the position that he desires to attain.

Patented Mar. 8, 1955 It will be clear from the above description that the belt material 1 must be of an unusual nature to serve the desired end. Unlike prior-art paper products and the like, the material must be capable of maintaining its shape such that with continued rotation or movement of the belt 1, the belt does not appreciably permanently stretch. Such stretching would, of course, slacken the mounting of the work sheet 3 upon the belt 1 and would also introduce considerable play at the roller 7 at the time of rotation of the mechanism 37. For the same reasons, the belt must not, furthermore, be appreciably affected by temperature or humidity changes and the like. Not only must the belt 1 be of such material that it substantially maintains a constant shape, but also it must be of a flexible nature in order that it may pass easily over the rolls 7 and 9 with rather sharp radii. The belt, of course, must not crack and it must be resilient enough so that it indents easily under the pressure of a pencil or pen in order that the lines drawn on the work sheet 3 shall be of the proper quality. Once the belt indents, however, it must have a high coeflicient of restitution so that it is able quickly to regain its shape after indentation. This is to be further contrasted with the before-mentioned prior-art belts in which the indentations remain permanently in the belt. The belt should resist tearing upon the penetration and movement of compass points and the like and it should preferably have the further property of self-sealing the holes made by compass-points and the like, as otherwise successive use of the compass point at particular locations will make very pronounced permanent holes. The belt, furthermore, should be capable of being easily cleaned in order that it may have long life. It has been found that there are some materials which, though providing some of these desired features, cannot be utilized as belt material because they do not possess others of the necessary requirements. It has been discovered that unless a certain rather critical relationship exists between the modulus of elasticity and the density of the material of the belt, the material is not suitable for use with the present invention. The modulus of elasticity is of itself very im ortant in determining the ease with which a belt matenal of normal belt thickness will stretch, flex over the rolls, absorb indentations and restore itself to original form. It has been found that this critical region lies between the region of paper and paper products, on the one hand, and metallic products, on the other. Those materials lying within the critical region are plastic materials having certain limits of density and modulus of elasticity. For best results in connection with the use of drafting instruments, moreover, the surface hardness of the successful plastic materials has been found preferably to lie within a further critical range.

Referring to Fig. 12, the ratios of the modulus of elasticity-to-density of different belt materials are plotted along the ordinate as a function of the density of the materials plotted along the abscissa. The density is expressed in terms of grams per cubic centimeter and the modulus of elasticity in terms of pounds per square inch. it will be observed that the point F on the lefthand side of the dash-dot graph line represents the region or area of paper material and paper products, having a density of the order of 0.7 and a modulus of elasticityto-density ratio of the order of 1,400,000. Though not indicated in Fig. l2, cork products are also on this lefthand side of the graph. The reasons for the unsuitability of paper and paper products, cork products and the like have previously been discussed. At the right-hand side of the graph of Fig. 12 a point G is plotted that represents the area of metalized belt material such as, for example, aluminum of about 0.03 inches thickness. Such material has a rather high density of the order of 2.7 and a modulus of elasticity-to-density ratio of the order of 3,700,000. The metalized material is also unsatisfactory because of its high density and extreme surface hardness. It has been found, however, that plastic products having densities within the shaded region of from about 0.85 to about 1.42. and modulus of elasticity-to-density ratios of less than about 600,000 are satisfactory in varying degrees for the purposes of the present invention. These materials have been found to possess the characteristics necessary to permit them to be used as a belt in the present apparatus, satisfactorily maintaining their shape under tension and under reasonable temperature and humidity changes, flexing about the sharp radii of curvature of the rollers, satisfactorily resiliently responding to the pressure of pencil points and the like, recovering from such pressure, and positively holding compass points and the like. in addition, the light-reflecting qualities of such surfaces have been found to assure satisfactory light diffusion. The point B in Fig. 12 represents the average of a large number of the successful plastic products, and the dash-dot curve of Fig. 12 demonstrates that the successful plastic products of the present invention occur at a minimum point B between paper and related products and metalized products. Among the most satisfactory of the materials within the shaded region are those plastic materials having a modulus of elasticity-to-density ratio of from about 10,000 to about 20,000, such as the following plastic composition: polyvinyl chloride (or polyvinyl acetate, or a copolymer of polyvinyl chloride and polyvinyl acelate) 60%, plasticizers 2030%, and stabilizers, pigments and lubricants l020%; unplasticized or slightly plasticized polyethylene; and polyvinyl butyrate 60%, plasticizers 20-35%, and stabilizers 520%. Point A in Fig. l2 represents the above-mentioned polyvinyl chloride or polyvinyl acetate plastic composition having a density of about 1.2 and a modulus of elasticity-to-density ratio of about 15,300. The point C represents the polyethylene plastic above-mentioned, having a density of about 0.88 and a modulus of elasticity-to-density ratio of about 14,700. The above-discussed polyvinyl butyrate plastic material is similar in properties to the polyvinyl chloride plastic. The points D and E represent the practical limits beyond which the materials are unsuited for the purposes of the present invention. The left-hand upper limit D of the critical region represents a plastic having a modulus of elasticity-to-density ratio of about 600,000, and the point E represents the right-hand limit having a modulus of elasticity-to-density ratio of about 320,000. These limiting regions may be obtained, for example, with partially polymerized and partially chlorinated or fluorinated polyethylene on the one hand, and Ker :1 slightly plasticized polyvinyl acetate, on the other While it has been determined that the plastic products within the shaded region of Fig. 12 have appropriate surface hardness as well as flexibility for the purposes of the present invention, the most satisfactory plastic products of this group, previously mentioned, having substantial self-sealing properties and resistance to tearing upon penetration by a sharp point, have been found to have a surface hardness between about 35 and 50 units as measured on the Rockwell Mscale. It is also most desirable that the belt material have a thickness of between about 0.02 and 0.25 inch, preferably being from about to $5 of an inch thick.

Utilizing plastic materials of the nature before described, the belt 1 has been found to last for long periods of time without the necessity for replacement. It is easily cleaned by washing with soap and water. The belt may be formed by securing. as by stitching, at the two ends of the plastic material, cloth strips provided with a zipper, inasmuch as there is little give in the zipper con struction and the plastic is quite resistant to tearing, as before stated. Directly stitching or clipping the ends of the belt material together may, however, be effected if desired. The belt material 1, furthermore, may be provided with a non-stretching cloth fabric or other backing. adding further rigidity to the compounded material, and therefore allowing a slight diminution in the thickness of the plastic material utilized. While these belt materials are admirably suited to the purposes of the belt system, it is to be understood that their properties make them most useful. also, as coverings for stationary drafting boards. as well.

It remains to describe the manner in which the angles 2 carrying the board 17 and the belt 1 may be adjusted and supported upon a surface such as the floor. The vertical portions of these steel angles 2 are shown provided with a plurality of slots 41 and holes 43 through which bolts. screws or other securing means may be passed to secure the lens or other supporting structure of the apparatus to the frame. The apparatus preferably utilizes metal tubular-leg side supports that may be bent into somewhat U-shaoe with the sides 6 of the U substantially vertical and the neck of the U flattened as at 14 to serve as a horizontal base. Rubber collar cushions 8 may be disposed about the lower horizontal gortionlofthelegstopreventmarringthefloor.

elescopicallyfitted withinthelegportionsiateach sideoftheframezarestanchions 10. 'Iheright-hand stanchion, as viewed inFig.1,issecured totheframe Zbyaboltpassingthroughoneoftheholesfltothe left of the auxiliary roller 11. The other stanchion is secured within the innermost slot 41. The stanchions 10 may be raised or lowered withinthe tubular side supports or legs 6 and may be secured in place by set screws 12 passing through cap fittings 46, more clearly shown in Fig. 2. With this construction, the frame 2 may thus be elevated at any desired height and at any desired angle or slope.

A tubular T-fitting 16 connects the central region of the bottom portion l4.of the legs 6 with a diagonal tubular brace 5. 1 The fitting is continumls about the tubular portion 14, but is lit into halves and secured by a bolt 16' passing throu one end of the tubular brace 5. The other end of the brace 5 is connected by a further T-fitting 16 to the intermediate region of a horizontal tubular cross brace 18, the ends of which are also provided with T-fittings 16 that connect with main tubular bracesZOdisposed parallelto the rolls 7,-9and 11. The

endsofthemainbraces20areconnectedbystillfurther T-fittings 16 to the side so rts or legs 6 mt below the set screws 12. The space tween the left d side supports or legs 6, as shown in Fig. 1, is left open in order that the legs and chair of the draftsman may be received under the angles 2 and belt 1. If it is desired, however, to orient the board at a very high angle of elevation or slope so that it isnecessary for thetowork in a standing position, the adjustable stanehions 10 may b I all th ugh hfi n drgd ilelgh de yorienting it ro one an ty grees, the stanchions 10 reconnected to the angles 2 through the slots 41, and the board elevated to assume the desired modulus of elasticityhigh an e of elevation. An adjustable tubular foot rest 22 at ed to the side supports 6 by similar T-fittings 16 is provided to permit the draftsman to rest his feet thereupon as he operates upon the highly elevated board.

Modifications will occur to those skilled in the art,

and all such are considered to fall within the spirit and.

scope of the invention, as defined in the appended claims.

What is claimed is:

1. A drafting member provided with a drafting board and a plastic surface for the board havingia density of between about 0.85 and 1.42 a ratio of modulus of elasticity-to-density substantially equal to or less than about 600,000, where the modulus of. elasticity is exthe density inunitsofpoundspersquareinchand In units of grams per cubic centimeter, and a surface andhardneasn on the Rockwell M-scal' e of between about 2. A drafting member provided with a drafting board and a plastic surface for the board having a thickness of between about 0.02 and 0.25 inch, a density of between about, 0.85 and 1.42, a ratio of modulus of elasticity-todensity substantially equal to or less than about 600,000, where the modulus of elasticity is in units of pounds per square inch and the density in units of grams per cubic centimeter, and a surface hardness on the Rockwell M-scale of between about 35 and 50.

3. A drafting member provided with a drafting board and a plastic surface for the board having a density in the neighborhood of about 1.2 and a ratio of modulus of elasticity-to-density of between about 10,000 and 20,000, where the modulus of elasticity is expressed in units of pounds square inch and the density in units of grams per cu ic centimeter.

4. A drafting member provided with a drafting boardand a plastic surface for the board selected from the group consisting of polyethylene, polyvinyl chloride, polyvinyl acetate and polyvinyl butyrate and having a density of between about 0.85 and 1.42 and a ratio of modulus of elasticity-to-density less than about 600,000, where the modulus of elasticity is expressed in units of pounds persquareinchandthe densityinunitsofgramsper cubic centimeter.

5. A drafting member provided with a drafting board and a plastic surface for the board of polyvinyl chloride having a density in the neighborhood of about 1.2 and a ratio of modulus of elasticity-to-density of between about 10,000 and 20,00f0, who; the modulus month elastlictiltiy is e ressed in units 0 poun square an e density inunitsofgramspercub z centim where the modulus of is group of polyethylene, polyvinyl chloride, polyvinyl acetate and polyvinyl butyrate and having density of between about 0.85 and 1.42 and a ratio h m odl r were em uusoe munits poundspersquareinchandthedensityinunitaof per cubic centimeter, the material having a surface hardness on the Rockwell M-scale of between about 35 and 50. 7. A drafting member provided with a drafting bfltlscard and a plastic ygait-the board aelectedmfi'umdc group consisting ene, polyvinyl polyvinyl acetate and polyvinyl and having a density of between about 0.85 and 1.42 and a ratio of modulus of elastidty-todensity less than about 600,-

0.082 5 inch. ha bmahon ngapparatus ving,incom",a drafting board, rollers supported spaced from opposite board, and an endless drafting belt disposed about the rollers over and under the board, the belt being of plastic material having a density of be tween about 0.85 and 1.42 and a ratio of modulus of eIasticity-to-density substantially equal to or less than about 600,000, where the modulus of elasticity is expressedinunitsofpoundspersquareinchandthe density in units of grams percubic centimeter.

9. Drafting apparatus having, in corn on, a drafting board, rollers supported spaced from oppodte ends of the board, and an endless drafting belt dis- 1 lwithout fthel rollers overaland under the board, ae t ing 0 pastic materi having a density of i tween about 0.85 and 1.42 anda ratio of modulus of elasticity-to-density substantially equal to-or lea than about 600,000, where the modulus of elasticity is expressed in units of pounds per square inch and the density in units of grams per cubic centimeter, the thickness of the belt being between about 0.02 and 0.25 inch and the belt surface having a Rockwell M-scale hardness of between about 35 and 50.

ends of the board, and an endless drafting belt about the rollers over and under the board, the belt being of plastic material having a density in the neighborhood of about 1.2 and a ratio of modal of elasticity-to-density of between about 10,000 20,000, where the modulus of elasticity units'of pounds per square inch and units of grams per cubic centimeter.

ll. Drafting apparatus-having, m draftingboarrhro g apparatus In combination, a board, rollers supported from 91 endsofthe andanendlessdraftingbeltdistp ih g g s emteiineeieqed andpolyvinylllltynteantl sity of between about 0.85 and 1.42 and a ratio of modulus of elasticity-to-density substantially less than about 600,000, where the modulus of elasticity is expressed in units of pounds per square inch and the density in units of grams per cubic centimeter, the belt having a surface hardness on the Rockwell M-scale 01: between about 35 and 50.

14. Drafting apparatus having, in combination, a drafting board, rollers supported spaced from opposite ends of the board, and an endless drafting belt disposed about the rollers over and under the board, the belt being of plastic material selected from the group consisting of polyethylene, polyvinyl chloride, polyvinyl acetate and polyvinyl butyrate and having a density of between about 0.85 and 1.42 and a ratio of modulus of elasticity-to-density substantially less than about 600,000, where the modulus of elasticity is expressed in units of pounds per square inch and the density in units of grams per cubic centimeter, the belt having a surface hardness on the Rockwell M-scale of between about 35 and 50 and a thickness of between 0.2 and 0.25 inches.

15. Drafting apparatus having, in combination, a

ulus of elasticity is expressed in units of pounds per square inch and the density in units of grams per cubic centimeter, the thickness of the belt being between about 0.02 and 0.25 inch and the belt surface gigwingd asoltockwell M-scale hardness of between about References Cited in the file of this patent UNITED STATES PATENTS 1,465,857 Martin Aug. 21, 1923 l,896,923 Tevonian Feb. 7, 1933 2,327,963 Haas Aug. 24', 1943 2,554,599 Stovern May 29, 1951 2,632,975 Klabunde Mar. 31, 1953 

